Controlled Rellease of oxygen scavengers in cooling systems

ABSTRACT

Provided are compositions and methods for releasing oxygen scavengers into a coolant. The compositions include a controlled release component and an oxygen scavenger component which includes at least one oxygen scavenger. Methods and devices for releasing oxygen scavengers into a coolant are also provided.

RELATED APPLICATION

[0001] This application is a continuation in part of U.S. patentapplication Ser. No. 09/539,914 filed Mar. 31, 2000 the disclosure ofwhich is incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to devices and methods forproviding a controlled release of oxygen scavengers to coolant incooling systems, for example, but not limited to, such systems ininternal combustion engines, for example, diesel engines, opencirculating cooling systems such as cooling towers, and the like.

BACKGROUND OF THE INVENTION

[0003] It is well known that with extended use of a coolant the coolantdegrades resulting in a lessening of effectiveness of the coolant whichis usually a glycol based composition, for example, propylene glycol orethylene glycol.

[0004] The main cause of coolant degradation, particularly at hightemperatures, is oxidation of elements that comprise the coolant.Typically, air enters a cooling system due to “breathing” caused by theheating and cooling cycles in the cooling system which cause the coolantto expand and contract. As the coolant cools, a vacuum is created whichdraws air into the system.

[0005] Coolant degradation, for example, oxidative degradation of acoolant can be reduced or eliminated in some cases by closing thecooling system to an intake of air. However, this approach is notpractical in many cooling system applications.

[0006] Alternatively, oxidative degradation can be minimized oreliminated by adding to the coolant a substance that will scavenge (e.g.remove) oxygen that enters a cooling system. Since air may enter acooling system slowly and constantly over a long period of time, it ispreferable that protective amounts of oxygen scavenger be introducedslowly into the cooling system in amounts effective to remove or lessenthe oxygen concentration.

[0007] Therefore, there is a need for compositions, methods and devicesfor releasing oxygen scavengers and/or oxygen scavengers into thecoolant of a cooling system at a controlled rate in order to preventoxidative degradation of one or more components of a coolant in thecooling system.

SUMMARY OF THE INVENTION

[0008] New compositions, methods and devices for providing release,preferably controlled release, of at least one oxygen scavenger into acoolant of a cooling system have been discovered. The presentcompositions, methods and devices effectively provide for gradual,preferably sustained, and more preferably substantially controlled,release of a oxygen scavenger into a coolant, for example, a liquidcoolant. A liquid coolant may include an aqueous phase. The liquidcoolant may also include at least one freezing point depressant, such asat least one glycol; a liquid coolant which includes at least onefreezing point depressant and does not include an aqueous phase; and thelike. Examples of glycols which may serve as freezing point depressantsinclude, without limitation, propylene glycol and ethylene glycol.

[0009] The present invention provides for coolant additive compositionswhich include a controlled release component and a oxygen scavengercomponent. The present invention also provides for methods for releasingan oxygen scavenger component into a coolant which include the step ofcontacting an additive composition with a coolant. The controlledrelease component is effective to reduce the rate of release of theoxygen scavenger component into a coolant in a cooling system. Theoxygen scavenger component includes one or more oxygen scavengers.Examples of oxygen scavengers that may be included in the oxygenscavenger component are thiosulfite, thiosulfate, mercaptopropionicacid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite,sulfide, stannous, hydroxylamine or hydrazine or mixtures thereof.

[0010] Liquid oxygen scavengers such as hydrazine may require a specialcomposition and/or device in order to effectively remove oxygen from acoolant. For example, aryl amine compounds and other compounds disclosedin U.S. Pat. No. 3,983,048 may be useful in this regard.

[0011] Examples of hydroxylamines that are useful in accordance with thepresent invention include, without limitation, hydroxylaminehydrochloride, hydroxylammonium acid sulfate, N,N-diethylhydroxylamine,Hydroxylamine phosphate, N-Ethylhydroxylamine,N,N-Dimethylhydroxylamine, O-Methylhydroxylamine, O-Hexylhydroxylamine,N-Heptylhydroxylamine, N,N-Dipropylhydroxylamine, O-MethylN,N-diethylhydroxylamine, N-Octylhydroxylamine, O-EthylN,N-dimethylhydroxylamine, N,N-Diethylhydroxylamine hydrochloride,N-Methyl N-ethylhydroxylamine, O-Methylhydroxylamine phosphate,N-Butylhydroxylamine, N-Benzylhydroxylamine (β-Benzylhydroxylamine),O-Benzylhydroxylamine (α-Benzylhydroxylamine) andN,N-Diethylhydroxylamine acetate

[0012] The rate of release of the oxygen scavenger component may bereduced relative to the rate of release of an identical compositionwithout the controlled release component.

[0013] The controlled release component may include, for example, amatrix material and/or a coating material. The matrix material and/or acoating material may be effective to reduce the rate of release of theoxygen scavenger component into the coolant relative to an identicaloxygen scavenger component without the provided coating material. Inaddition, the controlled release component may include one or morepolymeric materials. Further, the controlled release component may bepartially soluble in the coolant.

[0014] The oxygen scavenger component, when released in the coolant, iseffective to provide at least one benefit to the coolant and/or coolingsystem. In one embodiment, the oxygen scavenger component is effectiveto inhibit degradation of the coolant when the oxygen scavengercomponent is released into the coolant in a cooling system. For example,the oxygen scavenger component may be effective to inhibit oxidativedegradation of the coolant.

[0015] In accordance with the present invention, the coolant additivecomposition may be employed in a cooling system that is a circulatingcooling system. In one embodiment, the circulating cooling system is notcompletely closed.

[0016] In one embodiment, the cooling system cools an internalcombustion engine, for example, a diesel engine.

[0017] The present invention provides for methods of producing theherein described coolant additive compositions. In one embodiment,methods include the step of combining a oxygen scavenger component witha matrix material to form a mixture wherein the matrix material iseffective to reduce a rate of release of the oxygen scavenger componentinto a coolant in a cooling system.

[0018] In another embodiment the methods include the steps of: 1)providing a coolant additive composition which includes a oxygenscavenger component; and 2) providing a coating material on the coolantadditive composition to form a coated additive composition. The coatingmaterial may be partially coolant soluble and effective, when the coatedadditive composition is contacted with a coolant, to reduce the rate ofrelease of the coolant additive composition into a coolant in a coolingsystem.

[0019] The present invention also provides for combining methods ofproducing additive compositions, for example, a method which includesthe steps of: 1) combining a oxygen scavenger component with a matrixmaterial to form a mixture wherein the matrix material is effective toreduce a rate of release of the oxygen scavenger component into acoolant in a cooling system; 2) providing a coating material on themixture to form a coated mixture. The matrix material and coatingmaterial being effective to reduce the rate of release of the additivecomposition into a coolant in a cooling system.

[0020] The present invention also provides for methods for releasing aoxygen scavenger component into a coolant which include the step ofcontacting an additive composition produced by a method of the inventionwith a coolant.

[0021] The present invention also provides for coolant additiveassemblies. The present invention also provides for methods forreleasing a oxygen scavenger component into a coolant which include thestep of contacting an additive composition included in a coolantadditive assembly with a coolant.

[0022] The coolant additive assemblies may include a housing which mayinclude a coolant inlet and a coolant outlet. The housing may include anadditive composition disposed within the housing which includes acontrolled release component and a oxygen scavenger component. Thecontrolled release component may be effective to reduce the rate ofrelease of the oxygen scavenger component into a coolant in a coolingsystem.

[0023] Commonly assigned U.S. patent application Ser. Nos. 09/939,527;09/781,842; 09/939,214; 09/939,212; 09/539,914 and U.S. ProvisionalPatent Application No. 60/360,482 are directed to subject mattersomewhat related to the present patent application. The disclosure ofeach of these co-pending U.S. Patent Applications and Provisional PatentApplication is incorporated in its entirety herein by reference.

[0024] In addition U.S. Pat. Nos. 6,264,833; 5,024,268; 4,782,891;5,772,873; 5,803,024; 5,948,248; 6,290,870; 6,010,639; 3,962,109;3,959,166; RE37,369; 5,895,778; 4,711,735; 3,728,281; 3,808,138;3,687,610; 3,645,896; 4,079,018; 3,639,263; 3,983,048; 3,843,547;5,366,651; 4,655,930; 4,026,664 and European Patent Application EP1170348 are directed to subject matter somewhat related to the presentpatent application. The disclosure of each of these U.S. Patents and theEuropean Patent Application is incorporated in its entirety herein byreference.

[0025] Unless otherwise expressly noted to the contrary, each of thewords “include”, “includes”, “included” and “including,” and the phrase“for example” and abbreviation “e.g. ” as used herein in referring toone or more things or actions means that the reference is not limited tothe one or more things or actions specifically referred to.

[0026] Each and every feature described herein, and each and everycombination of two or more of such features, is included within thescope of the present invention provided that the features included insuch a combination are not mutually inconsistent.

[0027] Additional aspects and advantages of the present invention areset forth in the following description and claims, particularly whenconsidered in conjunction with the accompanying drawings in which likeparts bear like reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention is directed to the inclusion of an oxygenscavenger component in a coolant, for example, a coolant in a coolingsystem. The cooling systems, include, but are not limited to boilers,systems in or associated with motors, engines, such as internalcombustion engines, for example, in vehicles such as automobiles,planes, trains, trucks and the like, in heavy equipment, including bothstationary and mobile equipment, as well as open circulating coolant orcooling systems, such as cooling towers and the like.

[0029] In one broad embodiment, the present invention includes an oxygenscavenger component and a controlled release component.

[0030] The oxygen scavenger component may be any suitable compositioneffective for use in a coolant in accordance with the present invention.In one embodiment, the oxygen scavenger component is effective toeliminate or reduce the molecular oxygen concentration in coolants, forexample, in aqueous based or glycol based coolants. In anotherembodiment, the oxygen scavenger component is effective to eliminate orreduce the concentration of oxidative species in coolants, for example,in aqueous based or glycol based coolants. The oxygen scavengercomponent may be effective to prevent oxidative degradation ofcomponents present in solution or in dispersion in the coolant. Forexample, the oxygen scavenger components may prevent the oxidativedegradation of freezing point depressants such as glycols, glycol basedfreezing point depressants and the like, other coolant additives andmixtures thereof present in the coolant. The oxygen scavenger componentselected should be effective, as noted above, and have no substantial orsignificant detrimental effect on the coolant or the cooling system inwhich the coolant is used. In one embodiment, an oxygen scavengercomponent for use in accordance with the present invention is notintended, and preferably does not function, to form a protective complexwith metal to protect the metal from degradation, for example,corrosion. Examples of oxygen scavengers which can be included in anoxygen scavenger component include without limitation, thiosulfite,thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite,dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine andhydrazine and the like and mixtures thereof. In one embodiment, one ormore oxygen scavengers employed in an oxygen scavenger component is/areprovided as a salt. Examples of oxygen scavenger salts include withoutlimitation alkali metal (e.g., sodium or potassium), alkaline earthmetal (e.g., magnesium or calcium) ammonium and the like salts. Any andall combinations of the embodiments disclosed in the present inventionare included within the scope of the present invention.

[0031] Preferably, an oxygen scavenger component is released over aprolonged period of time, for example, under sustained conditions into acoolant, preferably a liquid coolant. The oxygen scavenger component iseffective when released into the coolant to confer or maintain one ormore benefits or beneficial properties to the coolant and/or the coolingsystem in which the coolant is used, in particular, the prevention ofcoolant degradation. The present invention may also be effective to, forexample, prevent corrosion in a cooling system.

[0032] Representative coolants include, but are not limited to, liquids,such as substantially an aqueous liquid including at least one freezingpoint depressant, such as at least one glycol, for example ethyleneglycol and/or propylene glycol; substantially a non-aqueous liquidincluding a freezing point depressant, such as at least one glycol, forexample ethylene glycol and/or propylene glycol; and the like.

[0033] The coolant may include one or more of the following: (1) abuffering component to maintain a neutral or alkaline pH, including forexample, alkali metal salts or sodium phosphates, borates and the like,(2) a cavitation liner pitting inhibitor component, including forexample, alkali metal or sodium nitrites, molybdates and the like, (3) ametal corrosion and hot surface corrosion inhibitor component, includingfor example, alkali metal, salts of nitrates, nitrates and silicates,carboxylic acids, phosphonic acids, phosphonate, pyrophosphate, azoles,sulfonic acids, mercaptobenzothiazoles, metal dithiophosphates and metaldithiocarbonates (one particular corrosion inhibitor that has been foundto be highly satisfactory is a phenolic anti-oxidant, 4,4′-methylenebis(2,6-di-tertbutylphenol) that is commercially available under thetrademark Ethyl 702 manufactured by Ethyl Corporation), and the like,(4) a defoaming agent component including for example, siliconedefoamers, alcohols such as polyethoxylated glycol, polypropoxylatedglycol or acetylenic glycols and the like, (5) a hot surface depositionand scale inhibitor component including for example, phosphate esters,phosphino carboxylic acid, polyacrylates, styrene-maleic anhydridecopolymers, sulfonates and the like, (6) a dispersing component,including for example, non-ionic and/or anionic surfactants such asphosphate esters, sodium alkyl sulfonates, sodium aryl sulfonates,sodium alkylaryl sulfonates, linear alkyl benzene sulfonates,alkylphenols, ethoxylated alcohols, carboxylic esters and the like, (7)an organic acid, including for example adipic acid, sebacic acid and thelike, (8) an anti-gel such as that disclosed by Feldman et al in U.S.Pat. No. 5,094,666, the content of which is incorporated in its entiretyherein by reference (for example, such anti-gel additive comprisescopolymers of ethylene and vinyl esters of fatty acids with molecularweight of 500-50,000; or Tallow amine salt of phthalic anhydride, usedat 0.01-0.2%; or Tallow amine salt of dithio benzoic acid, used at0.005-0.15%; or 4-hydroxy, 3,5-di-t-butyl dithiobenzoic acid; orethylene-vinylacetate copolymers) and/or microbiocides, for example,microbiocides used in open circulating cooling water systems of coolingtowers, as disclosed by Sherbondy et al. U.S. Pat. No. 5,662,803,wherein the disclosures of which is incorporated in its entirety hereinby reference.

[0034] In one embodiment, the controlled release component includes acoating or coating material encapsulating an oxygen scavenger componentcore which enables a reduced rate of release of the oxygen scavengercomponent into coolant in a cooling system, for example a circulatingcooling system. Preferably, the rate of release is reduced relative tothat of an identical composition without the coating material. Any typeof coating conventionally known in the art which providescontrolled-release properties may be used in the present invention.

[0035] A coated coolant additive composition may be of any size or anyshape to accommodate the circumstance of use. For example, compositionmay be in the form of a single object, for example a single,puck-shaped, or “doughnut” shaped object. In one embodiment, thecomposition is present as a plurality of irregular or regular shapedpellets or tablets. Different shapes and sizes, and the various surfaceto volume ratios provided thereby, can be selected to provide a desiredoxygen scavenger component release rate.

[0036] The coating or coating material may be soluble or partiallysoluble in the coolant. The soluble portion of the coating material maybe effective, when released into the coolant, to provide a benefit tothe coolant. Such coatings are highly advantageous in that they areeffective both to reduce the rate of release of the oxygen scavengercomponent into the coolant and to provide a further benefit to thecoolant when solubilized or partially solubilized into the coolant.Alternatively, the controlled release component, for example, a coatingmaterial may be substantially insoluble or insoluble in a coolant.

[0037] A coating material may constitute about 1% to about 60% of thetotal coolant additive composition weight. For example, the coating mayconstitute about 5% to about 48% or about 8% to about 30% of the totalcoolant additive composition weight.

[0038] In one particularly useful embodiment, the coating is a polymerdispersion. The polymer dispersion may have one or more the followingproperties:

[0039] 1. Viscosity: The polymer dispersion may be of a low to mediumviscosity. When the viscosity is to high, it may become impossible topump the polymer dispersion through a coating system. This may cause theline and spray gun to become plugged. Also, in this case, the dropletsof polymer dispersion may be too thick and difficult to lose moisture.They may not have the desired level of dryness before they reach thetablet surface. Therefore, the polymer may not form a good andhomogeneous coating.

[0040] It may be noted that reducing the viscosity of a polymerdispersion through dilution with water is not always a viable solution.Often the dilution leads to changes of physical properties for thepolymer dispersion and renders the polymer not appropriate for coatingapplications.

[0041] 2. Low film forming and glass transition temperatures: Everypolymer has its own characteristic film forming temperature and glasstransition temperature, T_(g). To form a good coating, the polymer mayhave a film forming temperature lower than the operating temperaturesinside the chamber of the drum coater in the coating process. A highT_(g) may lead to a brittle and fragile film which may easily peel off.Generally, a polymer with lower film forming temperature and T_(g) formsbetter film than those polymers with higher corresponding temperatures.

[0042] 3. Good film forming ability onto tablet surface: In the earlystage of coating process, the polymer may have good adherence to thetablet surface, so that the coating film can gradually build up. Thepolymer particles may pack well without large spaces or holes inbetween. This can be examined and confirmed under a microscope. Thepolymer with small particle size will result in better packing.Preferably, the polymer possesses good elasticity; otherwise, thecoating may crack, especially upon cooling.

[0043] 4. Insolubility of the polymer in an operating aqueous system:Typically, an operating aqueous system, has high temperatures. Forexample, an operating open circulating cooling water system may be about70 degrees F. to about 150 degrees F., for example, about 80 degrees F.to about 100 degrees F., or about 90 degrees F. to about 95 degrees F.The polymer coatings may remain insoluble and stable in these systems.If the polymer coating dissolves, it may lose the slow release function.

[0044] 5. Stability of polymer coating in solutions of aqueous systemsunder operating conditions: Many polymers degrade because they undergoalkaline hydrolysis reaction in operating aqueous system conditions. Asdegradation or dissolution occurs, the coating is damaged. As a result,the coating forms holes and loses the control of slow release.Subsequently, all chemical ingredients rapidly enter the bulk cooling.

[0045] Without wishing to limit the invention to any particularmechanism or theory of operation, it is believed that the release of theoxygen scavenger component from a coolant additive composition whichcomprises a polymer coating material into the coolant involves threesteps: (a) coolant enters the coolant additive composition through thepolymer coating; (b) chemical ingredients of the coolant additivecomposition dissolve in contact with cooling; and (c) the resultingconcentrated solution diffuses through the polymer coating back into thebulk of the coolant. The path and size of channels, microscopically,within the polymer coating, which are characteristics of each specificpolymer and are closely related to the physical properties of eachpolymer in coolant at elevated temperatures, may control the kinetics ofthese actions.

[0046] Suitable polymers useful in forming a controlled releasecomponent, for example, a coating material include, for example,homopolymers, copolymers and mixtures thereof, wherein the monomer unitsof the polymers may be derived from ethylenically unsaturated monomers,for example, two different such monomers.

[0047] A particularly useful ethylenically unsaturated monomer iscompound I with the formula (R₁) (R₂) (R₃)C—COO—(CH═CH₂), wherein R₁, R₂and R₃ are saturated alkyl chains. In one embodiment, R₃ of compound Iis CH₃, and R₁ and R₂ of compound I have a total of about 2 to about 15carbons; such a molecule is also known as a vinylversatate. In a oneembodiment, R₃ is CH₃, and R₁ and R₂ have a total of about 5 to about 10carbons. In another embodiment, R₃ is CH₃, and R₁ and R₂ have a total of7 carbons., i.e. R₁+R₂═C₇H₁₆.

[0048] In one embodiment, each of the R₁, R₂, and R₃ of compound I is asingle chemical element. For example, the element may be a hydrogen.Compound I having a hydrogen as the element for R₁, R₂ and R₃ is knownas vinylacetate.

[0049] In another embodiment, R₁ of compound I may be a single chemicalelement, and R₂ of compound I may be a saturated alkyl chain.

[0050] Other examples of ethylenically unsaturated monomers that may beused in accordance with the present invention include: monoolefinichydrocarbons, i.e. monomers containing only carbon and hydrogen,including such materials as ethylene, ethylcellulose, propylene,3-methylbutene-1, 4-methylpentene-1, pentene-1,3,3-dimethylbutene-1,4,4-dimethylbutene-1, octene-1, decene-1, styrene and its nuclear,alpha-alkyl or aryl substituted derivatives, e.g., o-, or p-methyl,ethyl, propyl or butyl styrene, alpha-methyl, ethyl, propyl or butylstyrene; phenyl styrene, and halogenated styrenes such asalpha-chlorostyrene; monoolefinically unsaturated esters including vinylesters, e.g., vinyl propionate, vinyl butyrate, vinyl stearate, vinylbenzoate, vinyl-p-chlorobenzoates, alkyl methacrylates, e.g., methyl,ethyl, propyl, butyl, octyl and lauryl methacrylate; alkyl crotonates,e.g., octyl; alkyl acrylates, e.g., methyl, ethyl, propyl, butyl,2-ethylhexyl, stearyl, hydroxyethyl and tertiary butylamino acrylates,isopropenyl esters, e.g., isopropenyl acetate, isopropenyl propionate,isopropenyl butyrate and isopropenyl isobutyrate; isopropenyl halides,e.g., isopropenyl chloride; vinyl esters of halogenated acids, e.g.,vinyl alpha-chlorocetate, vinyl alpha-chloropropionate and vinylalpha-bromopropionate; allyl and methallyl compounds, e.g., allylchloride, ally alcohol, allyl cyanide, allyl chlorocarbonate, allylnitrate, allyl formate and allyl acetate and the corresponding methallylcompounds; esters of alkenyl alcohols, e.g., beta-ethyl allyl alcoholand beta-propyl allyl alcohol; halo-alkyl acrylates, e.g., methylalpha-chloroacrylate, ethyl alpha-chloroacrylate, methylalphabromoacrylate, ethyl alpha-bromoacrylate, methylalpha-fluoroacrylate, ethyl alpha-fluoroacrylate, methylalpha-iodoacrylate and ethyl alpha-iodoacrylate; alkylalpha-cyanoacrylates, e.g., methyl alpha-cyanoacrylate and ethylalpha-cyanoacrylate and maleates, e.g., monomethyl maleate, monoethylmaleate, dimethyl maleate, diethyl maleate; and fumarates, e.g.,monomethyl fumarate, monoethyl fumarate, dimethyl fumarate, diethylfumarate; and diethyl glutaconate; monoolefinically unsaturated organicnitriles including, for example, fumaronitrile, acrylonitrile,methacrylonitrile, ethacrylonitrile, 1,1-dicyanopropene-1,3-octenonitrile, crotononitrile and oleonitrile; monoolefinicallyunsaturated carboxylic acids including, for example, acrylic acid,methacrylic acid, crotonic acid, 3-butenoic acid, cinnamic acid, maleic,fumaric and itaconic acids, maleic anhydride and the like. Amides ofthese acids, such as acrylamide, are also useful. Vinyl alkyl ethers andvinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether, vinyl propylether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl 2-ethylhexylether, vinyl-2-chloroethyl ether, vinyl propyl ether, vinyl n-butylether, vinyl isobutyl ether, vinyl-2-ethylhexyl ether, vinyl2-chloroethyl ether, vinyl cetyl ether and the like; and vinyl sulfides,e.g., vinyl beta-chloroethyl sulfide, vinyl beta-ethoxyethyl sulfide andthe like. Other useful ethylenically unsaturated monomers are styrene,methyl methacrylate, and methyl acrylate.

[0051] The coating material may be a mixture of polymers selected toachieve a desired release rate hardness and/or solubility. In oneembodiment, the polymer forming the coating is made up of a copolymer ofvinylacetate and vinylversatate. In a one embodiment, about 45% to about95% by weight of the units are from vinylacetate and about 5% to about55% by weight of the units are from vinylversatate. In one embodiment,about 65% by weight of the units are from vinylacetate and about 35% byweight of the units are from vinylversatate.

[0052] The vinylversatate used may be sold under the trademark VEOVA 10sold by Shell Chemicals. In one embodiment, the water-based emulsionpolymer is a vinylacetate-vinylversatate copolymer, sold under thetrademark EMULTEX VV575 sold by Harlow Chemical Co. (England).Additionally, a surfactant may also be added to stabilize thedispersion. In one embodiment, the polymer solid in the dispersion isabout 54% to about 56% by weight of active polymer solid.

[0053] EMULTEX VV575 is particularly advantageous because it meets allof the six requirements for a good coating as set forth above. That is,it (1) exhibits a viscosity low enough for coating processing withoutdifficulties, for example about 500 to about 1,500 mPa.s (RVT 2-20 at23° C.), (2) has a film forming temperature of 10 degrees C. and a glasstransition temperature, T_(g), of 11 degrees C., low enough for forminga good coating, (3) has a fine to medium particle size of 0.37 micronand forms an elastic coating, (4) is insoluble in coolings at operatingengine conditions, (5) is stable in coolings at operating engineconditions and (6) gives excellent release rates for ingredients.

[0054] In one embodiment, a copolymer which may be used as a coating inaccordance with this invention includes acrylate-vinylversatate. Forexample, NeoCAR 820 sold by Union Carbide may be used for formingcoatings.

[0055] A polymer forming a coating in accordance with this invention maybe made up of a copolymer of vinylacetate and ethylene. In oneembodiment, about 45% to about 95% by weight of the units are fromvinylacetate and about 5% to about 55% by weight of the units are fromethylene. In another embodiment, about 60% to about 80% by weight of theunits are from vinylacetate and about 30% to about 40% by weight of theunits are from ethylene. In still another embodiment, about 90% byweight of the units are from vinylacetate and about 10% by weight of theunits are from ethylene. A controlled release component of the presentinvention may advantageously comprise about 5% to about 15% of avinylacetate-ethylene copolymer.

[0056] A copolymer comprising vinylacetate and ethylene may be purchasedunder the trade name AirFlex 410, sold by Air Products and Chemicals,Inc., Allen Town, Pa., U.S.A. Such copolymer may have a viscosity ofabout 250 to about 900 cps.

[0057] In another embodiment, the polymer for coating is made up of ahomopolymer. The monomer unit of the homopolymer may be ethylcellulose.Ethylcellulose may be used for forming coatings is purchased from DowChemical sold under the trademark ETHOCEL S10, S20, S45 and S100.

[0058] Specific properties of the various ETHOCEL's are determined bythe number of anhydrous units in the polymer chain (expressed by themolecular weight or the solution viscosity), and, the degree of ethoxylsubstitution (expressed as the percent of hydroxyl group, —OH, incellulose substituted by ethoxyl group, —OC₂H₅). ETHOCEL S45 has asolution viscosity of about 41 to about 49 cP and about 48 to about49.9% ethoxyl content. The viscosity is for a 5% solution in 80/20toluene/ethanol measured at 25 degrees C. in an Ubbelohde viscometer.

[0059] Controlled release components may include a matrix material. Thematrix material may be effective to reduce a release rate of the oxygenscavenger component from the coolant additive composition into thecoolant, for example, relative to an identical coolant additivecomposition without the controlled release component. The level ofoxygen scavenger component in the circulating coolant is therebystabilized, maintained or replenished.

[0060] It is to be appreciated that a matrix material may comprise amaterial that is soluble or partially soluble in a liquid coolant. Forexample, a coolant additive composition in accordance with the presentinvention may comprise a coolant-soluble matrix material mixed with anoxygen scavenger component, wherein the soluble matrix material providessustained oxygen scavenger component release by gradually dissolvinginto the coolant, thereby gradually releasing the oxygen scavengercomponent located in the matrix material. Preferably, a suitable solublematrix material dissolves cleanly in the coolant without clogging orotherwise degrading components of the cooling system. In one usefulembodiment, the coolant soluble matrix material, when dissolved in thecoolant also functions as an additive, that is acts to provide at leastone benefit to the coolant. Alternatively, a matrix material may besubstantially soluble or substantially insoluble.

[0061] The matrix material may be effective to allow the coolantadditive composition to be compressed into, and maintain the shape of,for example, a pellet or tablet. Particularly useful such matrixmaterials include, without limitation, dispersants, polyvinylpyrrolidone, acrylates, for example, sodium acrylate and sodiumpolyacrylate, carboxymethylcellulose, metal carboxymethylcelluloses, forexample, sodium carboxymethylcellulose, hydroxypropylcellulose, metalhydroxypropylcelluloses, for example, sodium hydroxypropylcellulose,corn starch, microcrystalline cellulose, propylene glycol, ethyleneglycol, silicates, for example, sodium silicate and potassium silicate,methacrylate/acrylate copolymers, metal lignosulfonate, for example,sodium lignosulfonate and water.

[0062] In one embodiment, the matrix material includes one or morepolymeric materials. A suitable polymeric material for use in thecompositions of the present invention may remain stable in a hightemperature cooling system. In one embodiment, the polymeric materialhas a melting point in excess of the coolant operating temperature, forexample, a melting point in the range of about 50° C. to about 200° C.,or, for example, about 120° C. to about 150° C. or higher. In oneembodiment, the polymeric material is insoluble or partially soluble inthe coolant at the operating temperature of the cooling system.

[0063] The matrix material may be a viscous liquid, a gel or a solid.The matrix material, e.g., in a molten form or a soluble form, iscombined, for example, mixed with the oxygen scavenger component. Afterthe mixing step, the oxygen scavenger component/matrix mixture is formedinto one or more discrete units having irregular or regular shape andsize. The polymeric material may be at least partially soluble in thecoolant and, in one very useful embodiment, may be useful to provide abenefit to the coolant.

[0064] A coolant additive composition comprising a matrix material maybe of any size or any shape to accommodate the circumstance of use. Forexample, composition may be in the form of a single object, for examplea single, substantially spherical shaped or puck-shaped, or “doughnut”shaped object. In one embodiment, the composition is present as aplurality of irregular or regular shaped pellets, tablets, etc.Different shapes and sizes and the various surface to volume ratiosprovided thereby, can be selected to provide a desired oxygen scavengercomponent release rate.

[0065] Without wishing to limit the invention to any mechanism or theoryof operation, it is believed that when these discrete units of oxygenscavenger component/matrix material are placed in contact with coolantin a cooling system, the solid polymeric material serves as a physicalbarrier between the coolant and the oxygen scavenger component to limitthe rate of exposure of the oxygen scavenger component to the coolant,and thus reduce the rate of diffusion of the oxygen scavenger componentinto the coolant.

[0066] The polymeric material may include polymer repeating unitsderived from an olefin component having 2 to about 12 atoms permolecule. Such polyolefins are generally polymers of unsubstituted,aliphatic hydrocarbon olefins of 2 to about 12 carbon atoms, and aremore particularly polymers of an unsubstituted, aliphatic hydrocarbonolefin of 2 to about 12 carbon atoms and a substituted, aliphatichydrocarbon olefin of 2 to about 12 carbon atoms. In one embodiment, thepolymeric material is oxidized. In another embodiment, the polymericmaterial is amidized.

[0067] The matrix material may include an aliphatic acid component, forexample, as aliphatic acid component which includes aliphatic acidmolecules having about 18 or about 28 to about 36 carbon atoms. Aparticularly useful aliphatic acid component is montanic acid, nominallyC₂₈H₅₆O₂. Suitable aliphatic acid components, for example, montanicacids may have melting points from about 76° C. to about 87° C., forexample, about 76° C., to about 81° C. The aliphatic acid component mayhave a melting point of at least about 80° C. or at least about 82° C.Montanic acids with these characteristics are known, for example, underthe trade name S-Wachs.

[0068] Other polymeric materials are also capable of forming thecontrolled release component comprising, for example, a matrix material.These polymeric materials include: ethylcellulose, cellulose, silicones,rubbers, fatty and synthetic surfactants, thermoplastic resins,adsorbents (clays) and mixtures thereof.

[0069] Polyolefins may be prepared from unsubstituted, aliphatichydrocarbon monoolefins, including straight chain and branched chaincompounds such as ethylene, propylene and butene-1, isobutene, pentene,hexene, heptene, octene, isobutene, 3-methylbutene-1, 4-methylpentene-1,4-methylhexene-1, and 5-methylhexene-1.

[0070] The polyolefin may contain an unsubstituted, aliphatichydrocarbon polyene, such as diene or triene, as a monomer unit. Suchunsubstituted compounds can be straight chain, branched chain or cycliccompounds. In certain embodiments polyenes of from about 4 to about 12carbon atoms are employed.

[0071] Suitable comonomers for preparing the polyolefins are thoseutilized to prepare homopolymers as listed above such as propene orbutene-1 with ethylene or isobutylene with isoprene and the like.Suitable termonomers are those utilized to prepare homopolymers andcopolymers as disclosed above such as propene, ethylene and the likecontaining up to 15 percent, for example, up to about 10 percent byweight of polyene, for example, a diene such as dicyclopentadiene,1,3-butadiene, 1,5-cyclooctadiene, 2-ethylidenenorbornene-5, 1,4hexadiene, 1,4-heptadiene, bicyclo (2.2.1)hepta-2,5-diene and otherconjugated and especially non-conjugated dienes with linear or cyclicchains.

[0072] Trienes such as isopropylidene cyclopentadiene and theDiels-Alder mono- and di-adducts thereof with cyclopentadiene can beused in place of the diene.

[0073] Unsubstituted aliphatic diolefins can also be used for preparinguseful polyolefins such as butadiene, isoprene, octadiene, and the like.Especially useful are the various forms of polybutadiene, such as madein emulsion, suspension or solution processes, and random, block, andstar block polymers with monomers such as styrene.

[0074] In another embodiment, the polymeric material further includesdifferent polymer repeating units derived from an ethylenicallyunsaturated monomer. In one embodiment, such polymeric material ispolyethylene.

[0075] In one embodiment, the polymeric material is a copolymer ofethylene and vinyl acetate, for example, a polyethylene/vinyl acetatecopolymer sold by Dupont under its trademark ELVAX. Polyethylene/vinylacetate copolymer is able to withstand very high temperatures. Thepolymeric material may be a copolymer of ethylene and butylene.

[0076] In another embodiment, the polymeric material is polypropylene,for example polypropylene wax , e.g., having a molecular weight of about500,000. Such polypropylene is sold under the trademark Coathylene PY0787F. Other ethylenically unsaturated monomers includeethylene-propylene copolymers ranging in molecular weight from about200,000 to about 300,000; ethylene-ethylacrylate polymers ranging inmolecular weight from about 200,000 to about 300,000. A polyisobutyleneranging in molecular weight from approximately about 60,000 to about135,000 may be. Repeating units derived from an ethylenicallyunsaturated monomer used to form the polymeric material includes:monoolefinic hydrocarbons, i.e. monomers containing only carbon andhydrogen, including such materials as ethylene, propylene,3-methylbutene-1, 4-methylpentene-1, pentene-1,3,3-dimethylbutene-1,4,4-dimethylbutene-1, octene-1, decene-1, styrene and its nuclear,alpha-alkyl or aryl substituted derivatives, e.g., o-, - or p-methyl,ethyl, propyl or butyl styrene, alpha-methyl, ethyl, propyl or butylstyrene; phenyl styrene, and halogenated styrenes such asalpha-chlorostyrene; monoolefinically unsaturated esters including vinylesters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinylstearate, vinyl benzoate, vinyl-p-chlorobenzoates, alkyl methacrylates,e.g., methyl, ethyl, propyl, butyl, octyl and lauryl methacrylate; alkylcrotonates, e.g., octyl; alkyl acrylates, e.g., methyl, ethyl, propyl,butyl, 2-ethylhexyl, stearyl, hydroxyethyl and tertiary butylaminoacrylates, isopropenyl esters, e.g., isopropenyl acetate, isopropenylpropionate, isopropenyl butyrate and isopropenyl isobutyrate;isopropenyl halides, e.g., isopropenyl chloride; vinyl esters ofhalogenated acids, e.g., vinyl alpha-chloroacetate, vinylalpha-chloropropionate and vinyl alpha-bromopropionate; allyl andmethallyl compounds, e.g., allyl chloride, ally alcohol, allyl cyanide,allyl chlorocarbonate, allyl nitrate, allyl formate and allyl acetateand the corresponding methallyl compounds; esters of alkenyl alcohols,e.g., beta-ethyl allyl alcohol and beta-propyl allyl alcohol; halo-alkylacrylates, e.g., methyl alpha-chloroacrylate, ethylalpha-chloroacrylate, methyl alphabromoacrylate, ethylalpha-bromoacrylate, methyl alpha-fluoroacrylate, ethylalpha-fluoroacrylate, methyl alpha-iodoacrylate and ethylalpha-iodoacrylate; alkyl alpha-cyanoacrylates, e.g., methylalpha-cyanoacrylate and ethyl alpha-cyanoacrylate and maleates, e.g.,monomethyl maleate, monoethyl maleate, dimethyl maleate, diethylmaleate; and fumarates, e.g., monomethyl fumarate, monoethyl fumarate,dimethyl fumarate, diethyl fumarate; and diethyl glutaconate;monoolefinically unsaturated organic nitriles including, for example,fumaronitrile, acrylonitrile, methacrylonitrile, ethacrylonitrile,1,1-dicyanopropene-1, 3-octenonitrile, crotononitrile and oleonitrile;monoolefinically unsaturated carboxylic acids including, for example,acrylic acid, methacrylic acid, crotonic acid, 3-butenoic acid, cinnamicacid, maleic, fumaric and itaconic acids, maleic anhydride and the like.Amides of these acids, such as acrylamide, are also useful. Vinyl alkylethers and vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether,vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl2-ethylhexyl ether, vinyl-2-chloroethyl ether, vinyl propyl ether, vinyln-butyl ether, vinyl isobutyl ether, vinyl-2-ethylhexyl ether, vinyl2-chloroethyl ether, vinyl cetyl ether and the like; and vinyl sulfides,e.g., vinyl beta-chloroethyl sulfide, vinyl beta-ethoxyethyl sulfide andthe like can also be included as can diolefinically unsaturatedhydrocarbons containing two olefinic groups in conjugated relation andthe halogen derivatives thereof, e.g., butadiene-1,3;2-methylbutadiene-1,3, 2,3-dimethylbutadiene-1,3; 2-methylbutadiene-1,3;2,3-dimethylbutadiene-1,3; 2-chlorobutadiene-1,3;2,3-dichloro-butadiene-1,3; and 2-bromo-butadiene-1,3 and the like.Mixtures of the foregoing compounds can also be employed. Particularlyuseful monomer compositions also include styrene, methyl methacrylate,methyl acrylate, vinyl acetate, mixtures of styrene and acrylonitrile,and mixtures of styrene and various maleates.

[0077] In one embodiment, the matrix material may be a mixture ofpolymers selected to achieve a desired release rate, hardness and/orsolubility. Such mixtures may include, for example,polyethylene/polypropylene, and/or ethylene/butylene. The controlledmatrix material may further serve as a structural agent to the coolantadditive composition by retaining the shape of the composition.

[0078] To form an oxygen scavenger component/matrix coolant additivecomposition in accordance with the present invention, an oxygenscavenger component may be physically mixed with the matrix material inmolten form and allowed to solidify in a mold. In another example asolid (e.g., a powder) oxygen scavenger component may be mixed with asolid (e.g., a powder) matrix component and the mixture is pressed intoa shape, for example a pellet.

[0079] In one embodiment, the matrix material may be a one-component ormultiple component cure. For example, a monomer with catalyst or a twopart polymer, such as an epoxy or urethane, that is mixed with theoxygen scavenger component and will polymerize and harden to a solid.

[0080] In one embodiment, a controlled release component, for example amatrix material is partially soluble in the coolant. The controlledrelease component may include a portion which is soluble in the coolantand is effective when released into the coolant, for example, whensolubilized into the coolant, to provide a benefit to the coolant. Thus,the matrix material may be effective not only to reduce the release rateof the oxygen scavenger component into the coolant, but in addition, canalso act as an additional additive component in that the coolant isprovided with a benefit when the soluble portion of the controlledrelease component is released into the coolant.

[0081] In accordance with the present invention, the controlled releasecomponent may be a matrix material and/or a coating material. In oneembodiment of the invention, the coolant additive composition of thepresent invention includes an outer coating material which encases thediscrete units of oxygen scavenger component/matrix material. Thepolymeric material or materials used to produce the controlled releasecomponent (e.g. matrix material and/or coating material) can be selectedor chosen so that a portion of the polymeric material or materials inthe controlled release component is soluble in the coolant. Thematerials included within the controlled release component can becustomized to provide the desired degree of coolant solubility and adesirable benefit to the coolant when the soluble portion is solubilizedin the coolant. Such partially soluble controlled release components areincluded within the scope of the present invention. If the coatingmaterial is coolant-insoluble, the coating may be sufficiently porous,or breakable when exposed to high temperature coolant, to allow thecoolant to penetrate or break the coating and contact the oxygenscavenger component/matrix material encased therein.

[0082] If both a matrix material and a coating material are present, therelease rate of the oxygen scavenger component from the coolant additivecomposition may be reduced relative to an identical coolant additivecomposition without one of the matrix material and the coating material.

[0083] In one embodiment, the coolant additive composition is layered.For example, the innermost core of the coolant additive composition maybe a mixture of an oxygen scavenger component and a first matrixmaterial. The next layer of the coolant additive composition may be amixture of an oxygen scavenger component and a matrix material differentfrom the first. Alternatively, the next layer may be a mixture of theoxygen scavenger component and the matrix material of the first layer,but having a different mixture ratio. The coolant additive compositionof the present invention may include more than one layer to achieve avaried release pattern. In one embodiment, the coolant additivecomposition comprises more than two layers. In another embodiment, thecoolant additive composition comprises more than three layers. Suchlayered coolant additive composition provides for a variable releaseprofile, for example, a pattern of release varying between low and high.For example, the coolant additive composition may include an outer layerstructured to provide a minimal, low level rate of oxygen scavengerrelease and an inner layer structured to provide a relatively higherrate of oxygen scavenger release.

[0084] Other arrangement schemes may serve to vary the release patternof the oxygen scavenger component. For example, an additive compositionof the present invention may comprise an oxygen scavenger componentwhich is mixed with a matrix material which is then formed into discretepellets, which are then mixed with another matrix material and thenformed into a unitary object sized and shaped to be placed within acoolant line of a cooling system.

[0085] In one embodiment, a coolant additive composition of the presentinvention may further include a release enhancer component to increasethe release rate. A release enhancer component may be selected fromwicking materials, surfactants, for example, non-ionic surfactants,e.g., polyoxyethylene-polyoxypropylene block copolymers and the like,and mixtures thereof. Such wicking materials may include, withoutlimitation, cotton and polyester fibers and mixtures thereof. The fibersprovide a wicking mechanism for exposing coolant to inner portions ofthe coolant additive composition.

[0086] In one embodiment, a coolant additive composition of the presentinvention may further include a reinforcement component to reinforce thestructure of the coolant additive composition, making it lesssusceptible to erosion by flowing coolant. Such a component may include,for example, fibers, for example, cotton, polyester and/or fiberglassfibers.

[0087] Release-enhancer components and reinforcement components may beadded to the matrix material and or coating material. For example, oneor more of these components may be added to a matrix material prior to,or during, mixing of the matrix material with the oxygen scavengercomponent.

[0088] The rate of release of the oxygen scavenger component may beadjusted by the relative percentage of matrix material to oxygenscavenger component. For example, more matrix material content in thecoolant additive composition generally may reduce the rate of oxygenscavenger component release. In one embodiment, the matrix materialconstitutes about 1% to about 99% of the total coolant additivecomposition weight. In a one embodiment, the matrix material constitutesabout 25% to about 70%. For example, the matrix material may constituteabout 50% of the total coolant additive composition weight.

[0089] In the embodiment of the present invention in which thecomposition comprises a coated oxygen scavenger component/matrixmaterial composition, the rate at which the oxygen scavenger componentis to be released may be adjusted by the thickness of the coating and/orthe relative percent of matrix material content to oxygen scavengercomponent. For example, the coating material may constitute about 1% toabout 50% of the total coolant additive composition weight. For example,the coating may constitute about 8% to about 25% of the total coolantadditive composition weight. In addition, the matrix material mayconstitute about 5% to about 90% of the total coolant additivecomposition weight, for example, about 15% to about 70% of the totalcoolant additive composition weight.

[0090] The coolant additive composition may include a die release agent.Suitable die release agents include, for example, calcium stearate,magnesium stearate, zinc stearate, stearic acid, propylene glycol,ethylene glycol, polyethylene glycol, polypropylene glycol,polyoxypropylene-polyoxyethylene block copolymers, microcrystallinecellulose, kaolin, attapulgite, magnesium carbonate, fumed silica,magnesium silicate, calcium silicate, silicones, mono-and dicarboxylicacids and corn starch.

[0091] The coolant additive compositions of the present invention may bein the form of a single object, for example a single, puck-shaped, or“doughnut” shaped object. In one embodiment, the composition is presentas a plurality of irregular or regular shaped pellets, tablets, etc.Different shapes and sizes and the various surface to volume ratiosprovided thereby, can be selected to provide a desired oxygen scavengercomponent release rate.

[0092] In one embodiment, the coolant additive composition is in theform of a cylindrical tablet. The tablet may be of any size and anyshape. For example, the tablet may be about 9 mm length×about 9 mmdiameter. Alternatively, the tablet may be substantially cubical withall sides being about 9 mm. In yet another embodiment, the coolantadditive composition is a flat puck with a central aperture. The puckmay have, for example, an outside diameter of about 8 cm, an insidediameter of about 5 cm and a height of about 3 cm.

[0093] In one embodiment, release of an oxygen scavenger component intoa coolant in a cooling system may be achieved by use of a containerwhich includes a casing, for example, a coolant-insoluble andcoolant-impermeable casing, having or defining a substantially hollowinterior. The casing has at least one opening. The casing may have anysuitable shape and size, which are often chosen to be compatible withthe particular application involved. The casing, for example, may have agenerally cylindrical shape, a generally bowl shape or any of a largenumber of other shapes. The casing may have one or more curved and/orplanar walls or it can have all curved or planar walls. Further aspectsof containers that may be used in accordance with the present inventionare included in U.S. patent application Ser. No. 09/939,527 which isincorporated in its entirety herein by reference.

[0094] The coolant additive composition provided within a container ofthe invention comprises at least one oxygen scavenger effective whenreleased into the coolant to confer or maintain one or more benefits orbeneficial properties to the coolant and/or the cooling system in whichthe coolant is used. The coolant additive composition may be provided inthe form of a liquid, gel, paste or solid particles, for example, beads,tablets, pellets or grains, and the like, as well as mixtures thereof,within the casing. A coolant additive composition of the invention canadvantageously further comprise a coating material that at leastpartially surrounds or encapsulates or coats the oxygen scavengercomponent, as discussed elsewhere herein. Such coating material may beprovided in order to at least assist in controlling, or to control, therelease of oxygen scavenger component from the casing, as desired. Thecoating material may be either coolant-soluble or coolant insoluble. Thecoating on the oxygen scavenger component may be such as to allow orpermit at least some release of oxygen scavenger component from thecasing into the coolant.

[0095] The coolant additive compositions of the present invention may beprovided within a container and may include a matrix material. Thematrix material, if any, should be such as to allow or permit release ofthe oxygen scavenger component from the casing into the coolant. Thematrix material advantageously is effective to at least assist incontrolling, or to control, the release of the oxygen scavengercomponent into the coolant.

[0096] In one embodiment, the oxygen scavenger component is present inthe casing and no matrix material and no coating material are employed.In another embodiment, the oxygen scavenger component is present in thecasing and both a matrix material and a coating material are employed.

[0097] In one embodiment, a container for use in the present inventionmay include a coolant-permeable element or elements such as apolymer-containing membrane, for example, a polymer-coated membrane, inorder to achieve enhanced oxygen scavenger component release control.The membrane may be suitably coated, impregnated or otherwiseassociated, for example, by spray coating, dip coating and the like,with a polymer material. Suitable polymer materials include withoutlimitation, coolant insoluble materials which have no significantdetrimental effect on the coolant being treated, on the oxygen scavengercomponents in the casing or on the performance of the present container.Examples of such coating materials include those listed by Mitchell etal U.S. Pat. No. 6,010,639, the disclosure of which is incorporated inits entirety herein by reference. One useful polymer material ispolyethylene vinyl acetate copolymer. In addition, or alternatively, aretention member(s) of the coolant-permeable element or elements can becoated, impregnated, or otherwise associated with a material, forexample, a coolant-insoluble polymer material, such as those disclosedin Mitchell et al U.S. Pat. No. 6,010,639, to at least assist incontrolling or to control, release of the oxygen scavenger compositionfrom the casing, as desired.

[0098] In a one embodiment, a coating material can also be used to coatan aforementioned membrane of the invention. Moreover, a preferredrelease rate for oxygen scavenger component through the membrane can beprovided by adjusting the coating thickness to produce the preferredrelease rate. Suitable film forming polymers may include, for example,homopolymers, copolymers, and mixtures thereof, wherein the monomerunits of the polymers may be derived from ethylenically unsaturatedmonomers or cellulose derivatives.

[0099] A coating material is applied to the membrane by any suitablemethod. Certain methods include dipping, spray coating, and drum or pancoating. In one embodiment, a coating material is spray-coated onto themembrane in an amount ranging from about 1% to about 95% by weight ofthe membrane.

[0100] The container of the present invention may be filled with anoxygen scavenger component through the opening or openings of the casingor otherwise.

[0101] The containers of the invention, for example, the casings of thecontainers, may include one or more coolant-impermeable cap members orcoolant-impermeable plugs, which can be detachable or removable from thecasing or the remainder of the casing, for example, to facilitatefilling the interior space of the casing with coolant additivecomposition.

[0102] In one embodiment of the present invention wherein the casing issubstantially cylindrical shaped and the opening or openings are locatedat the end or ends of the casing, one or both ends of the casing mayinclude a cap member, with at least one of the cap members beingremovable to allow the casing or cartridge to be filled or refilled withcoolant additive composition. Another open end of the casing, ifdesired, may include a cap member that is permanently sealed thereto,for example, during manufacture, for example, during injection moldingof the container. Whenever the cap or plug is attached by threading orscrewing it onto the casing, screw threads can be applied to therespective pieces during or after molding with suitable dies or withinthe mold. The cap member can alternatively be applied to the casing by apress fit. In this case, suitable tolerances to make a snap fit betweenthe casing and the end piece can be provided, for example, to theplastic injection molds used to make the respective pieces. The endpiece can also be formed integrally with the casing, e.g., duringinjection molding.

[0103] The cap or end piece used to close at least one end of the casingcontaining the oxygen scavenger component typically is provided with atleast one opening to permit release of oxygen scavenger componenttherethrough, and to provide fluid communication between the coolantlocated exterior to the container and the coolant additive compositiondisposed within the casing interior. Whenever an end piece is formedintegrally with the casing, the opening can be provided therein duringor after formation of the casing, for example, by injection molding.

[0104] It will be appreciated by those of skill in the art that releaseof an oxygen scavenger component into a cooling system utilizing acontainer of the present invention is provided, and the release rate maybe substantially controlled by several factors. The following factors,as well as others, may also have an effect on the performance andeffectiveness of the containers of the present invention. For example,where a membrane is used, a desired oxygen scavenger component releaserate may be obtained by appropriate selection of: the number and type ofmembrane layers; membrane thickness; membrane composition; surface areaof the membrane; membrane pore size, if any; the presence, type andamount, if any, of polymer associated with, e.g., coated, on a supportmember or membrane and/or retention member; and the presence, type andamount, if any, of the matrix material in and/or coating on the oxygenscavenger component, if any. The rate of release may also be influencedby the number and size of openings in the casing, the type and form ofoxygen scavenger in the coolant additive composition, solubility of theoxygen scavenger, coolant temperature, and velocity of coolant throughthe coolant line, viscosity of oxygen scavenger component and/or coolantadditive composition, surface tension and membrane wetting ability ofthe oxygen scavenger, operating temperature and the like factors.

[0105] Contemplated within the invention is a method for releasing anoxygen scavenger component at a controlled rate into a liquid coolant.The method comprises placing a coolant in contact with a coolantadditive composition. In one embodiment, a coolant contacts a coolantadditive composition which is contained in a container or cartridge asdescribed herein. The container or cartridge configuration describedherein preferably permits a release, preferably a controlled release, ofoxygen scavenger component from the casing interior into the coolant. Itis contemplated that, in some configurations, coolant is permitted toflow around and encircle the casing containing the oxygen scavengercomponent. However, even in these configurations, release of oxygenscavenger component is preferably sustained and/or controlled, forexample, by passive diffusion, rather than by forced flow of coolantthrough the casing.

[0106] A oxygen scavenger component for use in a container or cartridgeof the invention may be provided as a liquid, gel, paste or asparticles, for example, beads, tablets, pellets, grains, coated versionsof these, and the like, as well as mixtures thereof. The particles havea physical size large enough to prevent passage through thecoolant-permeable components of the invention as described elsewhereherein.

[0107] A solid coolant additive composition of the present invention maybe shaped and sized in a manner that facilitates its handling, andconveniently is molded in the form of a pellet or tablet having aspherical or irregular shape. It may be large enough to avoid passingthrough porous components, if any, used to retain the oxygen scavengercomponent composition in the casing of the container.

[0108] Such tablets or pellets can break apart upon exposure to coolant,however, in certain embodiments, the fragmented particles are retainedby a porous component, with dissolution occurring inside the vessel.

[0109] In one embodiment, a concentrated solution of oxygen scavenger isformed within the container, which is permitted to pass, e.g., diffusethrough a membrane as desired for combining with the coolant. The rateof diffusion is controlled by parameters including flow rate andtemperature of the coolant, pore size, orifice diameter, the presence orabsence of a coating material on the porous membrane, the presence orabsence of a membrane, the inclusion of a plug between the membrane andoxygen scavenger material to further restrict release, oxygen scavengercomponent solubility and the presence or absence of a coating materialand/or matrix material, and the like. Each dimension of length, widthand thickness of the particle may be in the range from about {fraction(1/32)} inch to about 3 inch. Suitable binders may be used, as known inthe art, and include water-soluble acrylates, cellulosics, polyglycols,and silicates. The coolant additive composition may include one or moreadditional materials used, for example, to strengthen, stabilize and/orotherwise enhance the composition.

[0110] A device of the present invention can be placed in a coolantfilter, either upstream or downstream of the filter medium, or it can beprovided in a substantially fixed position in a coolant line, eitherupstream or downstream of a coolant filter.

[0111] The invention will now be described with reference to certainexamples. These examples are non-limiting and serve only to illustratecertain aspects of the present invention.

EXAMPLES Example 1 Oxygen Scavenger Added to a Commercial Coolant atSpecified Intervals

[0112] A commercial coolant based on propylene glycol was placed in asealed, stainless steel vessel and stirred and heated to simulateoperation of an internal combustion engine. Periodically the vessel andcoolant were cooled and air was bubbled through the vessel to introduceoxygen in the coolant. Coolant samples were removed periodically andanalyzed for test parameters indicative of coolant degradation (pH,reserve alkalinity, glycol oxidation products and corrosion inhibitors).In this first experiment, the values for these parameters at the end ofthe test were similar to those of coolant used in a diesel engine for200,000 to 300,000 miles. The coolant was no longer considered suitablefor use.

[0113] In a second experiment, the same type of coolant was subjected tothese same conditions except that the vessel was kept sealed and no airwas allowed to enter the system. In this case, coolant degradation wasnot detectable.

[0114] In a third experiment, the same type of coolant was againsubjected to the same conditions as described for the first experimentexcept that sodium sulfite, an oxygen scavenger, was added to thecoolant at specified intervals. Coolant samples were removedperiodically and analyzed for test parameters indicative of coolantdegradation. The values for these parameters at the end of the testshowed much less degradation of the coolant than in the firstexperiment. These results demonstrate that use of an oxygen scavenger inan engine coolant has the beneficial effect of decreasing thedegradation of the coolant.

Example 2 Forming a Coolant Additive Composition/Matrix MaterialComposition

[0115] One or more oxygen scavenger additive(s) in solid form, forexample, powder or granules, or in liquid form are mixed with a matrixmaterial comprising molten polyethylene wax. The materials are mixedonly long enough to distribute the oxygen scavenger additive(s) somewhatuniformly throughout the molten wax. The pellets or granules are notdissolved into the molten wax, but retain substantially their originalpellet or granular form. While in the molten state, the oxygen scavengeradditive/polyethylene wax mixture is then deposited into a mold to forma flat puck-shaped form, the puck-shaped form having a central hole anoutside diameter of 8 cm, an inside diameter of 5 cm and a height of 3cm. The mixture is allowed to solidify while in the mold and then thesolid puck-shaped composition is removed from the mold. Alternately, themolten oxygen scavenger additive/polyethylene wax mixture is cooled toform small pellets, which can be considered pastilles.

Example 3 Forming a Coated Coolant Additive Composition

[0116] A mixture of sodium sulfite and carboxymethyl cellulose iscompressed into pellets of about {fraction (1/32)} inch to about{fraction (1/16)} inch in diameter. The pellets are placed onto arotating pan inside a drum coater chamber. While the pan is rotated, adispersion of commercially available ethylene/vinyl acetate copolymer ispumped and sprayed through a nozzle onto the surfaces of the forms. Thespray rate is maintained at about 15 grams of dispersion per minute. Thespray pattern is controlled to give a good mist of copolymer droplets.

[0117] At the same time, through a very slightly reduced pressure, astream of warm air of about 40° C. is passed through the chamber toremove the water vapor from the polymer mist (or small droplets), beforeand after they reach the composition surfaces.

[0118] With time, the copolymer gradually forms a layer of coating oneach of the forms. After all copolymer dispersion is sprayed to reachthe desired thickness of coating, the resulting coated forms are allowedto stay on the rotating pan for a few more minutes, then are decantedfrom the pan into a container for storage.

[0119] Alternately, the solid which includes an oxygen scavengeradditive is coated with the copolymer in a spray drum coater.

Example 4 Forming a Coolant Additive Composition/Matrix MaterialComposition

[0120] The puck-shaped oxygen scavenger additive/matrix materialcomposition of Example 2 is coated with a coating material by placing aplurality of such puck-shaped forms onto a rotating pan inside a drumcoater chamber. While the pan is rotated, a dispersion of commerciallyavailable ethylene/vinyl acetate copolymer is pumped and sprayed througha nozzle onto the surfaces of the forms. The spray rate is maintained atabout 15 grams of dispersion per minute. The spray pattern is controlledto give a good mist of copolymer droplets.

[0121] At the same time, through a very slightly reduced pressure, astream of warm air of about 40° C. is passed through the chamber toremove the water vapor from the polymer mist (or small droplets), beforeand after they reach the composition surfaces.

[0122] With time, the copolymer gradually forms a layer of coating oneach of the forms. After all copolymer dispersion is sprayed to reachthe desired thickness of coating, the resulting coated forms are allowedto stay on the rotating pan for a few more minutes, then are decantedfrom the pan into a container for storage.

[0123] Alternately, the pastilles noted in Example 1 are coated with thecopolymer in a spray drum coater.

Example 5 Method of Using a Coolant Additive Composition/Matrix MaterialComposition

[0124] Several oxygen scavenger additive/matrix material compositionpuck-shaped forms of Example 2 are placed into a coolant filter canisterassembly during manufacture of the canister. In use, the coolant filtercanister is placed in fluid communication with a circulatingaqueous-based coolant system in a vehicle spark-ignited engine. Onceconnection has been made and fluid communication is established betweenthe cooling system and the canister, the coolant is circulated when theengine is running, allowing the aqueous-based coolant to contact theoxygen scavenger additive/matrix material composition forms disposed inthe canister. Upon contact with the forms, the high temperature coolantwill diffuse into and out of the polymer matrix material sufficiently torelease the oxygen scavenger additive into the coolant. The releasedoxygen scavenger additive dissolves in the circulating coolant. Thegradual release of oxygen scavenger additive, for example, at asubstantially uniform rate, continues during each circulation of coolantthrough the filter canister until, eventually, all oxygen scavengeradditive is depleted from the polymer matrix material. In this example,the canister includes filtering media for filtering coolant exiting thecanister and preventing larger particulate oxygen scavenger additivefrom entering the coolant system. The spent matrix material form isremoved from the circulating system by simply removing and properlydisposing the filter canister and thereafter replacing the canister withanother new filter canister containing oxygen scavenger additive/matrixmaterial composition forms produced in accordance with the presentinvention.

Example 6 Method of Using a Coated Oxygen Scavenger Containing CoolantAdditive Composition

[0125] Coated additive composition produced according to the method ofexample 2 is packed into a reservoir or housing connected, e.g., alongand in the fluid communication with an engine cooling system line. Anaqueous coolant is pumped through the cooling system line and throughthe packed reservoir. Upon contact with the high temperature coolant,the coating of the composition in the reservoir begins to soften andbreak, allowing the coolant to contact the oxygen scavenger additiveencased therein. The oxygen scavenger additive is released into thecoolant providing benefits thereto.

[0126] As an alternative to the coated additive composition disclosedabove, the ethylene/vinyl acetate copolymer coating is replaced with apartially soluble coating material. Upon contact with the hightemperature coolant, the coating of the cylindrical forms in thereservoir partially dissolves, releasing a portion of the coating intothe coolant to provide at least one benefit to the coolant. In addition,the coolant is able to penetrate the partially solubilized coating tocontact the coolant additive encased therein.

Example 7 Method of Using a Coated Oxygen Scavenger Containing CoolantAdditive Composition/Matrix Material Composition

[0127] Coated oxygen scavenger additive/matrix material compositionproduced according to the method of example 3 is packed into a reservoiror housing connected, e.g., along and in the fluid communication with anengine cooling system line. An aqueous coolant is pumped through thecooling system line and through the packed reservoir. Upon contact withthe high temperature coolant, the coating of the composition in thereservoir begins to soften and break, allowing the coolant to contactthe oxygen scavenger additive/matrix material encased therein. Theoxygen scavenger additive in the matrix material is released into thecoolant providing benefits thereto.

[0128] As an alternative to the coated additive/matrix materialcomposition disclosed above, the ethylene/vinyl acetate copolymercoating is replaced with a partially soluble coating material. Uponcontact with the high temperature coolant, the coating of thecylindrical forms in the reservoir partially dissolves, releasing aportion of the coating into the coolant to provide at least one benefitto the coolant. In addition, the coolant is able to penetrate thepartially solubilized coating to contact the oxygen scavengercomponent/matrix material encased therein. The oxygen scavenger additivein the matrix material is released into the coolant, providing benefitsthereto.

[0129] While the present invention has been described with respect ofvarious specific examples and embodiments, it is to be understood thatthe invention is not limited thereto and that it can be variouslypracticed within the scope of the following claims.

What is claimed is:
 1. A coolant additive composition comprising: acontrolled release component and an oxygen scavenger component whereinthe controlled release component is effective to reduce the rate ofrelease of the oxygen scavenger component into a coolant in a coolingsystem.
 2. The additive composition of claim 1 wherein the oxygenscavenger component is not effective to form a protective complex withmetal.
 3. The additive composition of claim 1 wherein the rate ofrelease is reduced relative to an identical composition without thecontrolled release component.
 4. The additive composition of claim 1wherein the oxygen scavenger component is effective to inhibit oxidativedegradation of the coolant when the oxygen scavenger component isreleased into the coolant.
 5. The additive composition of claim 1wherein the cooling system is a circulating cooling system.
 6. Theadditive composition of claim 5 wherein the circulating cooling systemis not completely closed.
 7. The additive composition of claim 1 whereinthe cooling system cools an internal combustion engine.
 8. The additivecomposition of claim 1 wherein the oxygen scavenger component isselected from the group consisting of thiosulfite, thiosulfate,mercaptopropionic acid, bisulfite, hydrosulfite, dithionate,hyposulfite, sulfite, sulfide, stannous, hydroxylamine and hydrazine ormixtures thereof.
 9. The additive composition of claim 1 wherein thecoolant is glycol-based.
 10. The additive composition of claim 1 whereinthe controlled release component is partially soluble in the coolant.11. The additive composition of claim 1 wherein the controlled releasecomponent includes a matrix material.
 12. The additive composition ofclaim 1 wherein the controlled release component includes a coatingmaterial.
 13. The additive composition of claim 1 wherein the controlledrelease component includes both a matrix material and a coatingmaterial.
 14. A method of producing a coolant additive composition,comprising the step of: combining an oxygen scavenger component with amatrix material to form a mixture wherein the matrix material iseffective to reduce a rate of release of the oxygen scavenger componentinto a coolant in a cooling system.
 15. The method of claim 14 whereinthe rate of release of the oxygen scavenger component into the coolingsystem is reduced relative to an identical additive composition withoutthe matrix material.
 16. The method of claim 14 wherein the oxygenscavenger component is effective to inhibit oxidative degradation of thecoolant when the oxygen scavenger component is released into thecoolant.
 17. The method of claim 14 wherein the matrix materialcomprises a polymeric material.
 18. The method of claim 14 which furthercomprises providing a coating material, the coating material beingeffective to reduce the rate of release of the oxygen scavengercomponent into the coolant relative to an identical oxygen scavengercomponent without the provided coating material.
 19. The additivecomposition of claim 14 wherein the oxygen scavenger component isselected from the group consisting of thiosulfite, thiosulfate,mercaptopropionic acid, bisulfite, hydrosulfite, dithionate,hyposulfite, sulfite, sulfide, stannous, hydroxylamine and hydrazine ormixtures thereof.
 20. The method of claim 14 wherein the cooling systemcools an internal combustion engine.
 21. A method of producing anadditive composition comprising the steps of: providing a coolantadditive composition which includes an oxygen scavenger component; andproviding a coating material on the additive composition to form acoated additive composition, the coating material being partiallycoolant soluble and effective, when the coated additive composition iscontacted with a coolant, to reduce the rate of release of the additivecomposition into a coolant in a cooling system.
 22. The method of claim21 wherein the rate of release of the additive composition is reducedrelative to an identical additive composition without the coatingmaterial.
 23. The method of claim 21 wherein the oxygen scavengercomponent is effective to inhibit oxidative degradation of the coolantwhen the oxygen scavenger component is released into the coolant. 24.The additive composition of claim 21 wherein the oxygen scavengercomponent is selected from the group consisting of thiosulfite,thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite,dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine andhydrazine or mixtures thereof.
 25. The additive composition of claim 21wherein the cooling system cools an internal combustion engine.
 26. Acoolant additive assembly comprising: a housing including a coolantinlet and a coolant outlet; and an additive composition disposed withinthe housing including a controlled release component and an oxygenscavenger component wherein the controlled release component iseffective to reduce the rate of release of the oxygen scavengercomponent into a coolant in a cooling system.
 27. The additive assemblyof claim 26 wherein the rate of release of the oxygen scavengercomponent into the coolant is reduced relative to an identical additivecomposition without the controlled release component.
 28. The additiveassembly of claim 26 wherein the controlled release component ispartially soluble in the coolant.
 29. The additive assembly of claim 26wherein the oxygen scavenger component is effective to inhibit oxidativedegradation of the coolant when the oxygen scavenger component isreleased into the coolant.
 30. The additive assembly of claim 26 whereinthe controlled release component comprises a coating on the oxygenscavenger component.
 31. The additive assembly of claim 26 wherein thecontrolled release component comprises a matrix material.
 32. Theadditive assembly of claim 31 wherein the matrix material comprises apolymeric material and is substantially coolant insoluble or ispartially coolant soluble.
 33. The additive assembly of claim 26 whereinthe controlled release component comprises a coating on the oxygenscavenger component and a matrix material.
 34. The additive compositionof claim 26 wherein the oxygen scavenger component is selected from thegroup consisting of thiosulfite, thiosulfate, mercaptopropionic acid,bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite, sulfide,stannous, hydroxylamine and hydrazine or mixtures thereof.
 35. Theadditive composition of claim 26 wherein the cooling system cools aninternal combustion engine.
 36. A method for releasing an oxygenscavenger component into a coolant comprising contacting the additivecomposition of claim 1 with a coolant.
 37. The method of claim 36wherein the oxygen scavenger removes molecular oxygen from the coolant.38. A method for releasing an oxygen scavenger component into a coolantcomprising contacting the additive composition produced by the method ofclaim 14 with a coolant.
 39. A method for releasing an oxygen scavengercomponent into a coolant comprising contacting the additive compositionproduced by the method of claim 21 with a coolant.
 40. A method forreleasing an oxygen scavenger component into a coolant comprisingcontacting an additive composition included in an assembly of claim 26with a coolant.